The first known vessels, detected in 1993, were semi-submersibles since they could not dive: most of the craft was submerged with little more than the cockpit and the exhaust gas pipes above the water. Newer narco-submarines are fully submersible, designed specifically to be difficult to detect visually or by radar, sonar and infrared systems.[2]

During the 1980s, go-fast boats became the drug-smuggling vessel of choice in many parts of the world.[1] These boats can be detected by radar; as radar coverage improved, Colombian drug cartels developed less easily detected semi-submersibles from the 1990s.[4]

The first time the U.S. Coast Guard found one, authorities dubbed it Bigfoot because they had heard rumors that such things existed, but none had actually been seen.[2] It was late 2006 when a Bigfoot was seized 145 km southwest of Costa Rica carrying several metric tonnes of cocaine.[5] In 2006, US officials say they detected three; in 2008, they were spotting an average of ten per month, but only one out of ten was intercepted. Few were seized, as their crews scuttle them upon interception and they sink within a minute or so.[6][7] By 2009, the U.S.A. detected as many as 60 narco submarine related events, and it was calculated that they were moving as much as 330 metric tonnes of cocaine per year.[8] Costing up to two million dollars each to construct, the submarines can move enough cocaine in a single trip to generate more than 100 million USD in illicit proceeds for the traffickers.[1][8]

Colombia's Pacific coastline, where muddy rivers loop into the ocean, has long been a smugglers' paradise. Behind the jagged cliffs that jut into the ocean is a vast jungle, laced with mangrove-fringed coves and virtually thousands of kilometres of waterways, apt for clandestine shipyards.[14] A Colombian Navy Commander stated that it is most striking to notice the logistical capacity required of these criminals in order to take all the material into the heart of the jungle, including heavy equipment such as propulsion gear and generators.[15] Sometimes they are put together in pieces and then reassembled in other locations under the jungle canopy, in camps outfitted with sleeping quarters for workers. The narco-submarines can cost about $2 million USD and take upward of a year to build.[15] Despite the costs, some of the craft are intended for one-time use, being abandoned at sea after a successful delivery. After all, their cargoes carry a street value of up to $400 million. On other seized craft however, officials found zinc bars used as sacrificial anodes, lessening corrosion on metal parts exposed to seawater.[16] As corrosion would not be a concern on a single trip but is a factor influencing long-term durability, this is a clear indication that multiple use was intended. This, in turn, opens up the question of any illicit return cargo, like weapons, that they might carry back to Colombia.

The design and manufacturing techniques employed in their construction have improved over time: the boats have become faster, more seaworthy, and of higher capacity than earlier models.[1] An 18 m long narco-submarine can reach speeds of 18 km/h and carry up to 10 tons of cocaine.[1] They are typically made of fiberglass, powered by a 225-260 kW diesel engine and manned by a crew of four. They have enough cargo space to carry two to ten tons of cocaine, carry large fuel tanks which give them a range of 3200 kilometers, [1] and are equipped with satellite navigation systems. There is no head (toilet), and accommodation is cramped.

Because much of its structure is fiberglass and it travels barely under the surface, the vessel is nearly impossible to detect via sonar or radar, and very difficult to spot visually. The newer models pipe their exhaust along the bottom to cool it before venting it, making the boat even less susceptible to infrared detection.[2] They are most easily spotted visually from the air, though even that is difficult as they are camouflaged with blue paint and produce almost no wake. They have ballast tanks to alter the vessel's buoyancy so that they ride low in the water.

Narco-submarines were considered by officials to be an oddity until 2000, when Colombian police discovered a true steel 30 m half-built submarine in a warehouse outside Bogota.[2][17] The double-hulled steel vessel could have traveled 3,700 kilometers, dive 100 m and could have carried 136 to 180 tonnes of cocaine.[citation needed]

On 3 July 2010, the Ecuadorian authorities seized a fully functional, completely submersible submarine in the jungles bordering Ecuador and Colombia.[3] This diesel electric submarine had a cylindrical fiberglass and Kevlar hull 31m long, a 3m conning tower with periscope and air conditioning. The vessel had the capacity for about 10 tonnes of cargo, a crew of five or six people, the ability to fully submerge down to 20m, and capable of long-range underwater operation.[3] Ecuadorean authorities seized the vessel before its maiden voyage.[18][19][20]

On 14 February 2011, another submarine was seized by the Colombian navy. The 31m long fibreglass and Kevlar vessel was found hidden in a jungle area in Timbiqui, in south-western Colombia. It was capable of travelling 9m below water and it could carry four people and up to 8 tonnes of cargo.[21]

In August 2005, U.S. authorities discovered an unmanned semi-submersible in the Pacific Ocean.[22] What they discovered was a "torpedo"-style cargo container (instead of a full-featured self-propelled ship). It used a ballast tank (submersion control) to keep it at about 30m under water while being towed by a boat. This particular "torpedo" was planned to be towed by a fishing vessel.[23] If a patrol ship is spotted, the "torpedo" cargo container is released. While still submerged, it was designed to automatically release a buoy (concealed as a wooden log so as to be mistaken for marine debris by authorities. This log-buoy was equipped with a location transmitter system. This allowed the original towing vessel to retrieve the torpedo if the vessel and her crew were released by authorities. If unable the original vessel was detained, or otherwise unable to retrieve the cargo torpedo, the location transmission system also allowed for a second support fishing vessel to retrieve it and continue the narcotics delivery. Such a log-buoy was designed to be used as a last resort, as there would be inherent risks involved with the deployment of said buoy. Authorities could notice the sudden appearance of the "log", and investigate. Additionally, authorities could have possibly picked up signals from the buoy's transmission systems, and may have attempted to locate such signal(s). Therefore, crew involved in the towing would be instructed to operate under the guise of a normal fishing vessel. Indeed, the intention would be to ensure no suspicions were aroused, thus avoiding the risks associated with deploying the log-buoy, by avoiding deployment altogether.

The buoy contains a mechanism to temporarily raise and then lower its antenna and transmit its coordinates in encrypted form a few times per day. Encrypted codes were used in the event that a buoy was deployed, and authorities intercepted its signals. Such an encryption could, at a minimum, delay authorities in their attempt to reach the cargo, ostensibly allowing the narco-traffickers to reach it first. This system was adapted from existing buoys used on tunafishing nets. One of its designers claims a 90% shipment delivery success rate, and stated that the "torpedo" development was heading towards a remote control feature using encrypted signals transmitted via satellite.[23]

A narco-submarine being seized by the U.S. Coast Guard off the Coast of Guatemala on September 17, 2008.

Narco-submarine moments before interception by the U.S. Coast Guard in August 2007.

Experts estimated that 25 to 40 cocaine semi-subs departed from South America in 2007, and expected that figure to double in 2008.[3] The western Colombian shore topography is near ideal for transporting the cocaine produced in clandestine laboratories in nearby Nariño department. About a third of the 550 metric tonnes of cocaine coming out of Colombia each year leaves via the Pacific coast and a significant amount is being carried in semi-submersibles.[24] The U.S. Homeland Security estimates that drug submarines now account for 32 percent of all maritime cocaine flow between Latin America and the United States.[25]

While the subs are most frequently used from the Pacific coast of Colombia, they are showing up elsewhere as well. The Coast Guard says drug runners have devised a complete logistics system, with fishing boats stationed along the way to warn the crews against patrols and provide them with food and water and resorting to putting refueling vessels far offshore so drug-carrying boats can avoid coastal areas.[26] For traffickers, reaching Mexico is well worth the trouble, as a 9 metric tonne load can fetch nearly US$200 million wholesale. Fishermen hired specifically for the task are often at the controls, and those who complete the trip successfully are paid about US$3,000.[2][23]

Smugglers normally unload their cargo onto fast power boats for the final leg to shore and the semi-submersible is scuttled. None have been sighted unloading at North American ports or beaches. In 2006, a 10 metre long sub was found abandoned on the northern coast of Spain, where the authorities suspect the crew had unloaded a cargo of cocaine before fleeing.[27] In March 2006, the Calabrianmafia ('Ndrangheta) ordered a shipment of 9 tonnes of cocaine to be transported by a narco-submarine from Colombia to Italy, but the vessel was discovered by the Colombian police while it was still under construction.[28]

During 2007, thirteen of the vessels were seized on Colombian dry land or stopped at sea by Colombian or U.S. patrol boats, more than in the previous fourteen years combined, but arrests are rare.[citation needed] When clandestine shipyards were discovered, workmen escaped into the jungle. In some instances semi-subs are towed behind other vessels and are scuttled if detected. Authorities are investigating reports that some semi-submersibles are unmanned and are operated remotely.

In the first six months of 2008, the U.S. Coast Guard and U.S. Navy detected 42 drug subs heading north towards the United States and off the coast of Central America,[29] but few seizures resulted. The service estimated that 85 individual events would bring in about 544 tonnes cocaine by the end of 2008.[30] As of 2007[update], the U.S. Coast Guard was adjusting its underwater acoustic sensors to listen to a narco-submarine's engine over long distances.[31]

On July 16, 2008, the Mexican Navy intercepted a 10 m-long narco-submarine travelling about 200 km southwest of Oaxaca. Mexican Navy Special Forces rappelled from a helicopter on to its deck and arrested four smugglers before they could scuttle their vessel. The vessel was found to be loaded with 5.3 tonnes of cocaine and was towed to Huatulco, Oaxaca, by a Mexican Navy patrol boat.[32][33][34][35][36]

On June 1 and 2, 2009 the Colombian authorities seized three narco-submarines on the shores of the Pacific coast, one of them loaded with 1.5 tonnes of cocaine.[41] The Colombian navy had intercepted or discovered 33 narco-submarines by 2009.[4]

When semi-submersibles are stopped at sea, their crews usually scuttle them, sending both the boat and the cocaine to the bottom in a minute or so and leaving no evidence of trafficking. Until 2008, in accordance with maritime law, the crew was rescued and, if there was no physical evidence of wrongdoing, released without criminal charges. To address this legal loophole, the US Drug Trafficking Vessel Interdiction Act was enacted in September, 2008, making it a "felony for those who knowingly or intentionally operate or embark in a self-propelled semi-submersible (SPSS) that is without nationality and that is or has navigated in international waters, with the intent to evade detection."[30] The penalty is a prison term of up to twenty years in the U.S.[42]

Some alleged narco-submarine smugglers are now facing criminal charges in the US for operating an unflagged semi-submersible.[44]

Colombia's Congress passed a law in June, 2009, punishing the building of semi-submersible vessels with up to twelve years in prison, and transporting drugs in them with up to fourteen years in prison.[43]

National security issues related to torpedo style cargo containers, semi-submersible vessels, and submarines used for smuggling and/or terrorist activities were reviewed in an August 2012 article in Homeland Security Affairs.[45] Also presented are behaviors indicating shifts in methods of operating by drug traffickers and the corresponding risk to national security.